Motor and brake device



Dec. 6, 1949 F. E. NIEDERHISER MOTOR AND BRAKE DEVICE Filed Sept. 16,1947 Q INVENTOR.

Patented Dec. 6, 1949 UNITED STATES PATENT OFFICE MOTOR AND BRAKE DEVICEFloyd E. Niederhiser, Cleveland, Ohio Application September 16, 1947,Serial N 0. 774,241

2 Claims. I

My invention relates to electric motor construction in general, and inparticular to variable power motors with brake means.

This application constitutes a continuation in part of my applicationfor Variable torque motor, Serial Number 635,227, filed December 15,1945.

Variable torque motors are generally used to position a driven objectwithin close limits. The power is adjusted to the desired amount, andturned off close to the desired stopping point. However, in recent yearssome applications have been developed which require a rather high torqueto start movement of the object, whereafter the object is loosened andis thereafter easily rotatable. The actuating mechanism of a lathe chuckis an example. To align a workpiece in a lathe chuck, the actuatingscrew of the chuck must be turned a determined amount and no more. Therefore, if a power wrench is used, the torque must be accuratelydetermined, and the rotation of the motor must be stopped within closelimits. If the motor is allowed to coast after the current has beenstopped, the actuating screw of the chuck will be turned too far and thechuck will be overcompensated and therefore will be out of line in theopposite direction. Furthermore, it is essential that the torque of themotor be accurately controlled in order to prevent crushing of aworkpiece. The braking mechanism is also useful in preventing thecontinuance of motor rotation which would tend to crush a lightweightworkpiece.

Therefore, an object of my invention is to provide an electric motorconstruction in which the rotor of the motor is adjustably exposed invarying degrees to the influence of an electrical field.

Another object of my invention is to provide an automatic brake devicewhich will be responsive to the magnetic field of the motor forreleasing the brake, and will be applied to stop rotation of the motorshaft upon cessation of the magnetic field.

Another object of my invention is the provision of an electrical statorand a rotor in an electric motor which may be adjustably varied withrespect to one another to control the amount of torque produced in therotor.

Another obiect of my invention is the provision of an electrical statorand a rotor in an electric motor which may be adjustably varied withrespect to one another to control the amount of torque produced in therotor, and a non-driving flux conducting member to conduct some of theflux across the flux field when the rotor and stator are movedlongtudinally apart and thereby stabilize the magnetizing current toprevent overheating.

A still further object of my invention is to provide a flux conductingmember on the shaft of a motor mounted for reciprocation upon the shaftbut non-rotative with respect to the shaft, which flux conducting memberwill be magnetically attracted to the rotor of the motor when the motoris in operation, and which will be movable away from the rotor when themotor field is unexcited, and therefore the flux conducting member willautomatically operate to actuate a brake device to stop the rotation ofthe shaft upon cessation of the exciting of the stator field.

Other objects and a fuller understanding of my invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawing, in which:

Figure l is a longitudinal cross-sectional view through a variabletorque motor of my improved design, and including my improved brakemechanism, with portions broken away for illustration: and

Figure 2 is a cross-sectional view through the line 2-2 of Figure 1.

Many industrial uses require power units and prime movers having theability to supply a driving torque in various degrees as desired. Tomeet this demand, industry has provided direct current machines andalternating current machines having controls thereon to control theamount of the voltage applied to the machines. Also,

various brush controlling devices and other cum-.

bersome equipment have been devised for this purpose. However, most ofthese devices are cumbersome and energy consuming, and at best, areexpensive and unsatisfactory for general application.

My improved invention is directed to the prob-- lem of supplying achosen amount of torque from a motor for a chosen period of time throughan extremely simple adjustable arrangement of the internal partsthereof, and to supplement the correct torque with quick and automaticstopping means.

Electric motors comprise basically wound stator to produce a revolvingelectrical field. Within the revolving electrical field, a rotor isemployed to be rotated by the influence of the revolving electricalfield. This rotor, then, in turn drives a shaft to supply mechanicalenergy. The stator of the machine produces a magnetic influence commonlyreferred to as the magnetic flux. This magnetic flux is easily conductedby certain types of metal, such for example as com 3 7 mon ironlaminations. Other mediums, such for example as air, are highlyresistant to the passage of the magnetic flux. Therefore, the amount ofspace between the rotatable rotor and the fixed stator is usually assmall as mechanically feasible, and the magnetic flux produced by thestator is readily induced into the rotor across the small air gapallowed. The stator generally comprises a laminated pack of iron sheets,and has a plurality of windings mounted thereon usually comprising manyturns of copper wire. The turns of copper wire induce the magnetic fluxinto the laminated stator pack rather than into the surrounding airbecause of the much better conductive-quality of the iron than the air.Therefore, the magnets flux will travel across the very small air gap-between the stator pack and the rotor and will be induced into the rotor.The"stator"pack"arid the rotor are generally of substantially the samelongitudinal length. Also, the torque produced by. the rotor isnecessarily dependent upon the amount of'the magnetic flux inducedtherein by the stator. Therefore, if therotor is so small that a'largeair gap is left between thestator pack and the'rotor, a greatlydecreased amount of flux Will be induced intothe rotorWith-proportionate reductionin the torque output of the motor.

My invention contemplates the longitudinal shifting of a rotor and astator pack with respect to one another in order to vary the amount ofmagnetic flux induced therein. However, although a simple longitudinalshifting of the rotor is entirely feasible and operable to limit theamount of magneticfiux induced therein, with a motor in which it isdesired to greatly reduce the amount of torque, and therefore in whichthe rotor will be moved a correspond-inglygreater distance, theremaining magnetic flux of the stator pack will attempt to enter intothe correspondingly smaller amount of the rotor remaining in adjacentrelationship thereto. That is, a greatly increased current flow Thisincreased flow, of course, if carried on for any lengthy period of time,will cause undue andexcessive heating in both the stator and the rotor.Therefore, in motors which are to be usedat considerably reduced torquecapacities, I- have provided for means to absorb the excess magneticflux over that which is desired to enter into the rotor, and therebystabilize the magnetizing current to maintain the electricalcharacteristics of the stator well within the limit of normal operatingconditions to prevent the undesired heating of both the stator and therotor.

V This means employed to absorber drain off the excessive magnetic fluxis preferably provided by a flux conducting member l which will'enterinto the revolving electrical field produced-by thestator when thestator is withdrawn. That is, as

the stator and rotor of the motor are shiftedlongitudinally with respectto one another, my invention contemplates the insertion of the fluxconducting member to fill the areain the revolving-electrical field thatwould be left vacant by the shifting. The flux conducting member i5 ispreferably of a material which will-readily conductthe magnetic flux,but is provided'in-such-a form that the absorption of the magnetic fluxwill notbe converted into rotativeforce to drive the shaft. Of course,there are-many ways in-which this might be accomplished, but I havefound-that" the preferable method is to provide a-fiux conducting memberof substantially thesame cross-- sectional outline as the rotoritself,and nonrotatively, but longitudinally shiftably mounted upon the motorshaft longitudinally adjacent to the rotor. Therefore, as thelongitudinal relaticnship of the rotor and the stator pack is changed,the flux conducting member it? will be in position to conduct a portionof the magnetic flux and correspondingly reduce the amount of themagnetic flux induced into the rotor, and thereby reduce the torqueoutput of the motor.

In the adaptation of my invention to practice, I have derived thepreferred embodiment, as illustrated inthe drawing. The embodimentillustrated in the drawing is considered to be the preferred embodimentbecause of its balance of utility and manufacturing cost. Theillustrated einbodimentsare not considered to be necessarily either themost ideal or the most economical embodiments. Rather, it is aconvenient balance of the two principles. Many other forms of the basicconception might well be employed with satisfying results.

With-reference to the Figure 1, I illustrate a motorframe It) to enclosethe working parts of a common polyphase A. C. motor. The motor operateson the basic principles of such electrical machines and includes astator l i mounted within a mounting ring l2 which is annular in form.The mounting ring 12, in the illustrated embodiment, is a continuousannular band in whichthe motor stator is held as a unit. That is, thestator H-may be moved and handled by the application of force to themounting ring 52.

Extending longitudinally of the motor frame in], is a shaft l3 suitablybearinged at either end in any convenient manner. A rotor i4 is carriedby the shaft l3 and-is secured thereto in such a manner that rotaryforce may be exerted by the rotor M to drive the shaft [3. Asillustrated, the rotor 54 comprises a conventional squirrel cageconcealed bar rotor. Of course, the illustrated squirrel cagerotor isused only for the purpose of setting forth my invention and is entirelyof conventional design. It may readily be replaced by other suitablerotors, either of the induction type orof-the wound externally excitedtype.

Asbest seen in the Figure 2, the motor frame it is formed to provide'twolongitudinal grooves diametrically opposite from one another on theinternalsideof the frame. These grooves are indicated by the referencecharacter I? and are employed to serveas a guide for a pair of grip armsIt. The grip arms It are of a hook-like nature and are adapted tointerfit across the mounting rings 12. That is, the longitudinal grooveI'l-servesas a base in which the grip arms it may be: longitudinallyslidably reciprocated, and'the griparms [6 in turn support the mountingring 52 which holds the stator H. Therefore, by moving'the grip arms ltlongitudinally within the grooves H, the entire stator it may bemoved-longitudinally within-'the motor frame [0."

The Figure 2 illustrates the means which I have" chosen tolongitudinally operate the griparms It. Two cross arms l8-= extendacross the frame it? and-interoonnect-thegrip arms 8%. Thus,

forceapplied to thecross arms 5-8 willserve to actuate the grip arms-l6and longitudinally shift comprises two plate members I9 each having agroove 49 therein as illustrated. Two drive arms 28 are provided, andare pivoted to the frame I by pivot pins 42. The drive arms 20interconnect with the plate members III by means of rollers 2!. Therollers 21 are adapted to operate in the grooves its to compensate forthe change in position of the free end of the drive arms 20 whenactuated by the toggle arrangement. Toggle arms 22 and 23, and links 25are pivotally secured together by a pin 24 to form a driver for thetoggle arrangement. The toggle arms 22 are pivoted to the drive arms 20by pins 43 intermediate the ends of the drive arms 20. Also, the freeends of the toggle arms 23 are pivotally secured to the motor frame Inby pins 44, as illustrated. Thus, force applied downwardly to the links25 will tend to increase the distance between the pivot pins 43 and 44and swing the drive arm 20 to the left from the position illustrated.Such movement will move the stator II toward the flux conducting memberI and away from the rotor H.

To conveniently apply moving force to the links 25, I have provided fora tubular member 25 to be threaded internall and be secured to the links25 by means of pins. An actuating screw 28 is threadably engaged to theinternal threads of the member 26 and is rotatabl moved by a suitableindex lever 29. A handle 31 on the lever 29 serves as a hand grip toturn the lever 29 and apply force to the toggle arrangement through themember 26 and the links 25.

In operation, therefore, the lever 29 may be rotated by means of thehandle 30 to move the links 25 and apply force to the pivotal connectingpoint between the toggle arms 22 and 23. From the position indicated inthe Figure 1, an movement of the pivotal connection between the members22 and 23 will tend to increase the distance between the pivot pins 43and M and cause the drive arms to move about the pivot pin 42 toward theleft in the illustration. In so moving, the drive arm ZG'will force thedrive connecting plate memoers E9 to move longitudinally of the motorframe id and push the cross arms I8 and the grip arms I6 therealong. Ofcourse, the grip arms It then move the motor stator longitudinallyrelative to the rotor I4.

It will readily be seen, with reference to the Figure 1 of the drawing,that any movement longitudinally of the motor frame It! by the stator IIwill cause the rotating electrical held produced by the stator I! to beshifted longitudinally towards the fiux conducting member l5.Immediately, an increased portion of the magnetic flux produced by thestator I I will be conducted across the short air gap into the memberI5. Thus, the flux entering the rotor M will be correspondingly reduced.If this movement of the stator II were continued until the stator IIwere positioned exactly correspondingly to the flux conducting memberI5, the power of the motor would be completely destroyed. Therefore, theindexing lever 29 may be suitably marked to indicate the appropriateposition to which it may be moved to cause the desired amount oflongitudinal movement of the stator I I. Thus, only a desired amount ofreduction in the torque of the motor will be produced.

In Figure l of the drawing, I illustrate the flux conducting member I5as being constructed of laminations held together by suitable rivets 36.The flux conducting member I5 is held against rotation relative to theshaft I3 by means of a 6 longitudinal key 38, but the key 38 allows theflux conducting member I5 to reciprocate longitudinally upon the shaftI3.

A brake shoe 3I is secured to the frame II and surrounds the end of theshaft I3. In other words, the brake shoe 3| is an annular membersurrounding the end of the shaft I3, and is pro-- vided with a flange31, having a brake surface on the end thereof. A suitable brakingmaterial 32 is secured to the end surface of the member I 5 by suitablerivets 34. Therefore, the rotation of the shaft I3 may be stopped bytightly pressing the flux conducting member I5 toward the brake shoe 3|to produce a high friction between the brake material and the brakesurface of the flange 3?.

I have provided three springs 33 to urge the member I5 toward the shoe Mto provide the braking action described. In the Figure 1, only one ofthe springs 33 is illustrated, because the Figure l is a straightcross-sectional view. The springs 33 are positioned degrees apart aroundthe member I5, and press against the rotor I4. Thus, by the pressureapplied to the fiux conducting member I5 by the springs 33 pressingagainst the rotor M, the brake material 32 is pressed against the brakesurface of the flange 31 and the shaft I3 is quickly stopped. The brakeshoe 3: and the fiux conducting merrber I5 thereb serve as brake meansto stop the shaft.

However, it will be noted that the member is positioned within the areaof magnetic fiux field produced by the windings iI. Also, the member I5is adapted to conduct magnetic Therefore, when current is passed throughthe windings II to operate the motor, the member will be attractedtoward the stator field. However, the distance Which the member i5 maymove is physically limited by the rotor Id. In Figure a clearance 35 isillustrated between the member I5 and the rotor I4. Therefore, themember i5 can move longitudinally against the urge of springs 33 on theshaft I3 the distance of the clearance 35. This movement will thenproduce a like clearance between the braking material and the brakesurface of flange 31. Therefore, the movement of the member i5 towardthe rotor I4 will release the member l5 and the shaft it for freerotation. However, immediatel upon cessation of current passing throughthe stator Ii, the magnetic attraction upon the member Iii Will cease,and the springs 33 will tightly press the material 32 against the brakesurface of the flange 3i and stop the rotation of the shaft I3.

By this improved combination of elements as described, I have provided avariable torque motor capable of being quickly and easily adjusted toprovide a desired torque, and which will automatically stop within avery short space of time when the current to the motor is turned off.All this is provided with the addition of very few parts more than aconventional electric motor. Further, the additions which have been madeare of such a construction that they are almost beyond the necessity ofever needing maintename, and certainly will not require any more servicethan a standard motor.

Although I have described my invention in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted 7 to. withoutdeparting: from the spirit:- and: the scope ofi'the invention ashereinafterclaimed.

I claim:

1. An adjustable torque andibrakable: electric motor comprising, aframe; a stator: adapted to produce a magnetic fiux field; a2.shaftrrotatably mounted in saidframe, a rotordrivingly mounted onsaidshaft insaidflux-field tddrive the shaft under the influence ofsaidt fiux field'g said' rotor having atleast one: radial plane 'surfacearea; a laminated flux conducting member mounted 'n'onrotatively andlongitudinally. reci'procably on' said shaft within the infiuence of'saidi'flux fieldj said flux conducting member having at lea'stone-radial plane surface substantially equal' in areato the said planesurface area ofth'e'rot'ori said plane surface area of thefluxconducting'member being placed relative=to said plane surface area ofthe rotor forcontact th'ereagain'st upon movement of the fluxconducting' membertoward said rotor, spring means adapted tonrge saidflux conducting member longit'udin'a'lly away from said rotor and'fluxfield; said'flux conduct-- ing member being'magnetically attractedtowardsaid flux field against the*urge'-of'said' spring means when saidfiuxfield is produced" by'said stator, shifting means to reciprocably shiftthe longitudinal position-of the-statorrelative' to the rotor and fluxconducting member, saidflux field thereby being at least partiallydiverted from'the rotor toreduce' the torque of the? motor and directedto the flux conducting'membertosta bilize the magnetizing current; abrake shoe mounted on said frame andh'avinga brakesufi face adjacentsaid flux conductingmember;said

flux conducting memberhaving'brake surfaces adapted to contact saidbrake surface of the brake shoe; Wh'ereby'said b'ra'ke surfacesmay" beurged apart by movement of thefl'iix conducting.

member toward said fluxfi'eldto allow" free rotation of thesh'aft;andsaitlbrakesurfaces' may be urged to contactbymovement'ofthefiuxiconducting movement away' from the flux field to,

stop the rotation of'th'e' shaft; I

25 An adjustable't'orque and"bra;l able electric motor'comprisingj aframe, a" stator adapted to.

produce a" magnetic flux field} a shaft. rotatably;

mounted in'sa'id frame a' rotor drivingly mounted on saidshaftinsaidfluxfield to. drivetlie shaft underthe influence ofsaidfluxfieldesaid rotor having at least" one, end? surface areaextending, generally" transversely of'the shaft, alaminated flu'xconducting member mounted non-rotatively and longitudinally reciprocablyon said shaft within the influenceof; said fiux field; said fluxc'onducting' member fh'avin'g atleast one end 'surf ace-area extendinggenerally transversely of f the shaft, said: flux-conducting memberhavinga diameter substantiallyequal a to the diameter of the rotor, saidendisurfacearea ofthe'flux conducting member facing said vend surface.area of theirotor, springimeans'adapted to urge-said fluxconducting'member: longitudinally away from said rotor; said; flux-conductingmember being magnetically attracted toward said flux field againstthe'urge of said'spring means when said flux field is produced by? saidstator, shifting means to recipro'c'ably shiftithe'longitudinalpositionof the statorirelativetothe rotor and'fii1x conducting member,vsaid flux field" thereby being at leastzpartially' diverted from therotor to reducethe torque of the motorfand directed' to the fluxc'onducting' member to stabilize the magnetizing current, a brake shoemounted on? said frame and having a brake surfaceadjacentsaidflux-conducting member, said flux-conducting member havingbra-kesurfaces adaptedto con-- tact saidbrake'surfaceof the brakeshoe, wherebysaid brake surfaces may be urged apart by movement of theflux-conducting membertowardsaid flux field? to allow free rotation ofthe shaft, and said brake surfaces may be urged to contact by movementof the flux-conducting movement away from the flux field to stop therotation of the shaft FLOYD E. NIEDERHISER;

REFERENCES CITED The following references are of record inthe:

file of this patent:

UNITED STATES PATENTS

